Low compression: Comments?

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Model T Ford Forum: Forum 2012: Low compression: Comments?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Sunday, June 03, 2012 - 05:56 pm:

With the timing gear installed to turn things, I tried a compression test. I squirted a little oil in each cylinder and turned the crank. Beginning with #1, the readings were 0, 39, 22, and 35. That 22 seems a little low to me. A quick perusal of the literature didn't turn up anything. The MTFCA book doesn't have an index, and the Ford index doesn't mention compression. Maybe some of you can steer me to the right pages. Before I dig in, any sage advice?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Kennedy on Sunday, June 03, 2012 - 06:12 pm:

I believe it is in the 55 psi range when working right. I would first check the valve adjustments and cam timing in relation to the crank. The throttle should be wide open when testing. Also, you should squirt a few ounces of motor oil into the cylinder and do a wet test just to verify the rings.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, June 03, 2012 - 06:16 pm:

0 seems even lower. I think you may have some technique issues.

A few technique questions -Did you have the throttle wide open? All four plugs removed? Turn the crank until the guage won't go any higher? All these things must be done to have repeatable, true readings.

I would NOT squirt oil in the cylinders first. That will give false (higher) readings.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Sunday, June 03, 2012 - 06:22 pm:

Steve,

The most important part about compression is that all cylinders be pretty close when done.The burn rate/expansion and compression have something in common.

35 is considered a good average number in a stock T, but people do manage to get higher. More 'expansion' = better burn rate.

I have seen T's go as low as 10-15 and still work. A little rough to get started, never win a road race, last one to get there, the 'putt-putt' T. Know of one where the compression is about 12 cold/15 hot, been that way for 25 years and it always gets there and back...last...but jokingly it has never overheated and never needed a get it later roadside. Not saying I'd run that low tho', I think it is a matter of pride for the guy now.

Now what can lead to low and variable compression? The head gasket may have a trace in it or not be tight enough, there can be blow-by on the rings and wear (why checking with oil in the cyls. can help show the way). Piston rings can get tighter under heat and help along with a good carbon coat on the walls :-) Then there is valve seating and valve timing.

That '0' could be a hung sticky valve, could be something else.

I'm not sure any Ford material really addresses 'compression' other than you need it. Good piston ring seat, sequence to torque head, valves lapped and seated, filing and drawing out valves to get a 'seat', etc. The trick is 'close' on all 4.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Sunday, June 03, 2012 - 06:23 pm:

oops...good average LOW number I meant


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Cassara Long Island, NY on Sunday, June 03, 2012 - 06:24 pm:

In general low numbers would be bad rings. Zero bad valves. You don't need ounces of oil, a tablespoonful (15ml) would be enough. You are looking for similar numbers not so much as a max number. It would run with 4 cylinders of 35psi but 50psi would be better. Others will comment with T specific numbers.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Kennedy on Sunday, June 03, 2012 - 06:25 pm:

I guess I should have specified doing the dry test first eh?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bernard Paulsen, San Buenaventura, Calif on Sunday, June 03, 2012 - 07:02 pm:

Remove all spark plugs.
Throttle wide open, which is easy on a T.
Test every cylinder when cold. Write down reading.
Repeat.
Repeat.
Now spray some oil in the lowest one or two cylinders.
Repeat once more.

Report back and we will systematically try to determine the reason for the low compression.

It's easy to get a false reading.

OT info: a few days ago, my daughter blew the head gasket on her 1992 Mercedes 190E. Looking for a cheap replacement car, a deal came up, a 2001 Saturn with the 2.2-liter Ecotec engine. Mileage (gasp) . . . 200K. Compression (I took it myself) 215/214/215/213. Unfrigginbelievable.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen D Heatherly on Sunday, June 03, 2012 - 10:02 pm:

Steve, are you sure both valves are completely closing on the cylinder that is reading zero? I would turn the engine over with the crank until one of the valves opens in the cylinder with zero compression and drip oil into the valve then do the same for the other valve and let it sit for a while. Then try the compression test again. Sometimes the valves will gum up in their guides and not close properly in an engine that has been sitting for a long period of time. Hopefully if this is your problem the oil will free them up. Also make sure that there is a gap between the pushrod and the valve stem when the piston is at top dead center at the end of the compression stroke. The cylinder with 22 PSI may have bad rings but sometimes the rings will stick in the ring glands and not seal against the cylinder walls properly. This is also caused by the engine not being run for a long period of time. Put a little oil in the cylinder and let it sit a while and see if it improves the compression. If all else fails you could remove the cylinder head to get a better idea of what is wrong.

Good luck,
Stephen


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Monday, June 04, 2012 - 12:13 am:

Steve, I think you should look at the valve clearances first. 0 is pretty low ... did you mean that? 22 could be carbon under one of the valves but, 0 is not good at all!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Monday, June 04, 2012 - 12:42 pm:

Bad valves, pull head, post pictures.

Sorry for the long winded rant.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Monday, June 04, 2012 - 02:13 pm:

The oil squirt is to check the rings. You do it "dry" then do it "wet". If the rings are slightly worn the compression usually goes up a bit because the oil provides a temporary ring seal. As to the 0 cylinder: this is USUALLY due to an open/burned/stuck valve. So what's first? Not the cylinder head. That may come later but the valve cover would be my first choice. It'll allow you to check the clearances and note if any are stuck. if the Gods are with you it'll be an adjustment. Good Luck.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, June 04, 2012 - 02:45 pm:

Are you sure the compression gauge is completely sealing and the valve in it is working? If so continue with the following checks. Did you check the compression before you started on your repair? Only if you knew what it was before, could you be sure that something you have done recently lowered the compression. The 0 would indicate one of the valves on cylinder #1 is sticking open. You need to find the reason. It could be sticky valve guide, weak or broken spring, keeper missing,or valve adjustment too tight. The others could be either bad rings or bad valves. A raise in compression after squirting oil will tell you the rings are worn. But if it is the same or nearly the same after squirting oil, something is wrong with the valves.

Next test would be to check valve timing to see if they open or close near the point which is shown in the manual. First try checking them with the valve cover off. That way you won't need to remove the head unless it is needed. If you know what the compression was before, and it dropped after you replaced the timing gear, It is possible that the marks were not lined up, either one tooth ahead or behind. Also check the valve clearance that every valve has 10 thousandths or more clearance. If too little clearance, your valve might not be closing completely. If these tests don't find the problem You could need to grind the valves.
Sorry about your problems.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, June 04, 2012 - 03:08 pm:


I think this may explain that zero on #1.
Looks to me like more than .010", so lack of clearance isn't the problem. The keeper is there and the spring is fine. Thinking maybe it was stuck, I lifted the valve and let it snap back. No change. Seems there's something stuck under the valve to keep it from seating. I'll try raising the valve and shooting in some air to see if I can blow out whatever is in there. If that doesn't help, I guess the next step is to pull the head and see what's going on in there.


Yes, the timing marks are fine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, June 04, 2012 - 05:50 pm:

So I lifted the valve to get it off of whatever might be under it, and blew compressed air in the spark plug hole. No change. Valve still not seating, still zero compression. Next step: Off with its head.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Monday, June 04, 2012 - 06:12 pm:

Jeff,
You may be able see something down the spark plug hole or if you take off the manifolds. I'm sure with the right light and device (mirror or endoscope you could see something.

Maybe a soft wire down the spark plug hole could dislodge some foreign object.

It would be a shame to take the head off if you don't need to.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Monday, June 04, 2012 - 06:13 pm:

Sorry, that should have been Steve.
Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Brumfield on Monday, June 04, 2012 - 06:27 pm:

1. The most accurate compression readings are obtained when the engine has been warmed to normal operating temperature before the test.

2. All spark plugs removed. (Squirt no oil)

3. Carb plates held in wide open position during test.

4. Start the check on No.1 cylinder.

5. Engine should be turned over at least 5 pumping strokes and record the highest reading. Note the approximate number of compression strokes required to obtain the highest reading.

6. Repeat the check on each cylinder cranking the engine approximately the same number of compression strokes.

If the readings are low, repeat the test using oil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Monday, June 04, 2012 - 06:59 pm:

Could be bent. We'll know soon.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Monday, June 04, 2012 - 10:40 pm:

Is it even possible to get a zero reading assuming the valves are sealing and the head gasket is OK ?

schuh


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Tuesday, June 05, 2012 - 01:04 am:

Bub,
Yes, it would be possible to get a zero reading assuming the valves are sealing and the head gasket is OK. One thing that would do it is a broken rod and maybe a large hole in a piston would be really close to zero.
Under normal conditions, even a badly burnt valve or broken rings will give a reading well above zero.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Tuesday, June 05, 2012 - 06:11 am:

STOP!

Don't pull the head just yet.
Most stuck valves can be tapped closed with a 1/4" aluminum rod through the spark plug hole.

Shoot your favorite penetrating oil down the valve and then exercise the valve by tapping closed and cranking the engine. Also, you can exercise the valve by using a long screwdriver suspended like an original Ford valve spring lifter and move valve up and down until the goop is sufficiently broken down that the spring does it's thing by itself. By the looks of the valve chamber, things are really gummy.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Cassara Long Island, NY on Tuesday, June 05, 2012 - 08:24 am:

Use care if you try to exercise the valve. Too much leverage may bend the valve. Lube the crap out of it and lift / lower it from the valve cover. If you get it to close / open properly a compression test will give you an idea as to it's true health!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, June 05, 2012 - 08:40 am:

If it still has old two piece valves they are better replaced anyway.
The broken off valve head syndrome seems like a more common failure now than it was back in the day, so perhaps it's a corrosion / age thing just like the śntrustworthy babbitt thrust washers in the rear?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Tuesday, June 05, 2012 - 09:56 am:

Taking off the manifolds revealed the secret.


It seems a puddle of water around the valve stem produced enough rust the make it stick.


So I squirted in a little oil.


Then raised the valve way up and let it down several times. That brought compression on #1 up from zero to 36 psi. Next I'll go to work on #3 and see if I can get that 22 psi any higher.

I wonder how water got in there. I doubt a head gasket leak because I don't think antifreeze would do this.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Tuesday, June 05, 2012 - 11:37 am:

Quote: "I wonder how water got in there"
Methinks it's probably condensation. Is this the one you only ran a bit and then the timing gear failed?

If you run any engine and shut it off before it's fully warmed up, you stand a good chance of condensation forming in the engine, usually in the cylinders or exhaust ports. If it's a daily driver it's not usually a problem, but if the vehicle is only used occasionally, that's where problems occur.

Another bad spot for condensation is in the muffler. Years ago mufflers always had a drain hole at the low point, but not any more. So, I just drill a 1/8" drain hole in the mufflers of our vehicles. Don't have to worry about emissions testing around here, if we did, to be on the safe side, I'd make sure I put a sheet metal screw in the hole before going in for testing.
No holes in the mufflers of our Ts though, I always try and make sure that any time they're started they run for at least a 1/2 hour, if not more.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Tuesday, June 05, 2012 - 11:56 am:

Say Steve, Isn't that the engine you flushed recently? Let's hope it water that leaked in around the exhaust gasket during your flushing process not a head gasket leak caused by the same process!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Tuesday, June 05, 2012 - 11:56 am:

I'm going to throw something out! Maybe it was the stuck valve that caused the timing gear to break. The valve being stuck made the camshaft bind and the binding of the cam shaft put a strain on the timing gear. Is that an exhaust valve? The exhaust valves tend to get quite hot and since it is at number 1 if the engine got hot and boiled, someone poured cold water in and it would go right down the hose and into the front of the block causing a crack. When you get the head off, check the valve seat around number 1 exhaust for cracks. They can usually be repaired. It might not have happened when the antifreeze was used, but might have happened a long time ago. Anyway, when you get the head off it's time to grind all the valves and fix any leaks you might find whether a gasket or a crack. Good luck, keep us posted.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Tuesday, June 05, 2012 - 12:46 pm:

I'm with John. Especially if it's the engine Jeff just flushed. Doesn't look like exhaust rings were used by the look of the ring land. There's a better chance of water getting into the valve cavity with out them. The first shot showing the puddle doesn't look like anti which I think he mentioned using in a later post. If the first shot is un touched and he used anti the water came from another source.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Schreiber- Aiken, SC on Tuesday, June 05, 2012 - 01:31 pm:

I believe this is for Steve's Fordor. The flush was on his 23 touring.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Tuesday, June 05, 2012 - 02:51 pm:

Gary is correct. This is the Fordor I brought home in March. It only ran a few minutes before the fiber timing gear went south. That would account for condensation in the exhaust port. Sitting still through the following couple of months would account for enough rust forming to keep the valve from going all the way down.

Here's a before picture showing the engine before I started it up and had the great timing gear adventure. A few observations on anomalies I've found so far.


Note the washers under the manifold clamps. The exhaust manifold sticks out farther than the intake manifold and the washers even that out for the clamps. I'll go through my pile of manifolds and see if I can find a better match.

Two different kinds of manifold clamps.

Antifreeze all over the fan belt and surroundings. The water pump is going bye-bye. (Maybe I'll send it to Royce.) If the radiator isn't up to snuff I'll get a new one.

The fan hardware is 26-27. I'm going back to stock 1923.

Charlie's observation on the manifold rings is close. They were there, but not tight. Compressed air blown in the spark plug hole came out around the exhaust manifold. I believe I'll clean things up and install new ones.

It looks like I may have some generator repair to do. The way you see it is the way it came.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Tuesday, June 05, 2012 - 09:17 pm:

You might want to make sure the manifold didn't shrink like the one on my '25 Fordor.
Clean up the ports on the head and manifold, put the rings in and see if it fits.
It SHOULD slip right in.
If it doesn't you might want to spend the $80 for a new one, junk the old one and save a lot of headaches.


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